Implement localhost prioritization and status display in dashboard

- Always select localhost as default host at startup
- Order hosts with localhost first, then predefined sequence
- Display hostname status colors in title bar based on metric aggregation
- Add gethostname dependency for localhost detection

dashboard/Cargo.toml

@@ -17,4 +17,5 @@ tracing = { workspace = true }
 tracing-subscriber = { workspace = true }
 ratatui = { workspace = true }
 crossterm = { workspace = true }
-toml = { workspace = true }
+toml = { workspace = true }
+gethostname = { workspace = true }